Implant devices secured to bone or bone segments are utilized to promote the healing and repair of various parts of the human body. In some cases, the implant devices are secured to the bone or bone segments such that the bones themselves heal, fuse, or stabilize relative to one another. In other cases, implant or fixation devices are used to secure bones or bone fragments so that the surrounding soft tissue may heal without disruption by relative movement of the bones.
During the surgical procedure to implant the fixation devices, a plurality of bone screws or other fixations elements are secured to a plurality of respective bones. Then, each of the bone screws is secured relative to the others with an additional apparatus, such as a connecting member or rod.
For example, spinal rods that immobilize vertebral bones of the spinal column are typically anchored to the vertebrae via bone screws that extend through the pedicle into the vertebral bodies or by hooks that engage about the vertebrae. The spinal rods are connected to the screws or anchor members by coupling members, which may be yoke-shaped. Such coupling members may be integral with the anchor member head or separate components from the anchor member.
While incisions are required during such surgical procedures in order to gain access to the site where the implant is secured, such incisions can cause damage, injury, and trauma to the patient's body. To avoid causing unnecessary damage, it is preferable to make the incisions as small and few as possible.
One prior approach to implanting a bony structure stabilization device uses an installation instrument with a pivoting brace inserter. To implant the connecting element, extensions are attached to the anchors and the installation instrument with the pivoting brace inserter being rigidly attached to the extensions. The pivoting brace inserter employs a fixed geometric relationship to guide the connecting element into position. The installation instrument mounts to the bone anchors extension and holds the connecting element such that when the instrument's pivoting arm is pivoted, the connecting element follows a direct predetermined path into position about the anchor. As the connecting element is swung into position, the element enters the body through the skin at a remote location removed from the surgical incisions made to attach the bone anchors.
This approach can be problematic because another incision or opening is made through the skin, in addition to the openings required to insert the two screws. This additional opening allows for insertion of the brace or rod. Further, because of the fixed path, such a system is unable to direct the connecting element along a path of least resistance through the soft tissues and thereby causes tissue trauma that could otherwise be avoided by the surgeon variably moving the connecting element around and between these tissues. In addition, if the patient's vertebrae are misaligned the surgeon can encounter difficulty when inserting the brace along predetermined path because the predetermined path may not account for the various vertebrae locations.
Another approach to the minimally invasive system utilizes the same pathway that is used to insert the spinal anchors to also insert the connecting element. The connecting element is then manipulated such that it shifts to a perpendicular orientation to the insertion pathway in order to connect the anchors. Positioning of the connecting element can be assisted by a manipulation tool but nonetheless remains relatively unguided relying significantly on surgeon skill and patience.
Accordingly, there is a need for a minimally invasive surgical system that limits the number and size of the incisions, minimizes trauma to the soft tissues, and also provides physicians with control to efficiently and effectively implant necessary devices.